Slightly improve error reporting

6 files changed, 115 insertions, 12 deletions

diff --git a/examples/hello.sloth b/examples/hello.sloth
index 619a5a0..8abb65c 100644
--- a/examples/hello.sloth
+++ b/examples/hello.sloth
@@ -1,5 +1,4 @@
 fn main() Int {
     print("Hello World\n");
-    var x: F = 2;
     return 0;
 }
diff --git a/sloth/src/lexer.rs b/sloth/src/lexer.rs
index 20379a3..01eeb46 100644
--- a/sloth/src/lexer.rs
+++ b/sloth/src/lexer.rs
@@ -2,6 +2,7 @@
 
 //! TODO: Lexing Regex Literals
 
+use std::fmt::Display;
 use std::str::Chars;
 
 use thiserror::Error;
@@ -112,6 +113,86 @@ pub enum TokenType {
     Error(LexerError),
 }
 
+impl Display for TokenType {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let s = match self {
+            TokenType::DocComment => "##",
+            TokenType::Comment => "#",
+            TokenType::OpeningParen => "(",
+            TokenType::ClosingParen => ")",
+            TokenType::OpeningBracket => "[",
+            TokenType::ClosingBracket => "]",
+            TokenType::OpeningBrace => "{",
+            TokenType::ClosingBrace => "}",
+            TokenType::Plus => "+",
+            TokenType::PlusPlus => "++",
+            TokenType::Minus => "-",
+            TokenType::Star => "*",
+            TokenType::StarStar => "**",
+            TokenType::Slash => "/",
+            TokenType::Perc => "%",
+            TokenType::Tilde => "~",
+            TokenType::PlusEq => "+=",
+            TokenType::PlusPlusEq => "++=",
+            TokenType::MinusEq => "-=",
+            TokenType::StarEq => "*=",
+            TokenType::StarStarEq => "**=",
+            TokenType::SlashEq => "/=",
+            TokenType::PercEq => "%=",
+            TokenType::TildeEq => "~=",
+            TokenType::Amp => "&",
+            TokenType::AmpAmp => "&&",
+            TokenType::Pipe => "|",
+            TokenType::PipePipe => "||",
+            TokenType::Caret => "^",
+            TokenType::Eq => "=",
+            TokenType::EqEq => "==",
+            TokenType::Bang => "!",
+            TokenType::BangBang => "!!",
+            TokenType::BangEq => "!=",
+            TokenType::Lt => "<",
+            TokenType::LtLt => "<<",
+            TokenType::LtEq => "<=",
+            TokenType::LtLtEq => "<<=",
+            TokenType::Gt => ">",
+            TokenType::GtGt => ">>",
+            TokenType::GtEq => ">=",
+            TokenType::GtGtEq => ">>=",
+            TokenType::Comma => ",",
+            TokenType::Question => "?",
+            TokenType::QuestionDot => "?.",
+            TokenType::QuestionQuestion => "??",
+            TokenType::Dot => ".",
+            TokenType::DotDot => "..",
+            TokenType::Colon => ":",
+            TokenType::ColonColon => "::",
+            TokenType::SemiColon => ";",
+            TokenType::Arrow => "->",
+            TokenType::FatArrow => "=>",
+            TokenType::Const => "const",
+            TokenType::Val => "val",
+            TokenType::Var => "var",
+            TokenType::Fn => "fn",
+            TokenType::Return => "return",
+            TokenType::If => "if",
+            TokenType::Else => "else",
+            TokenType::While => "while",
+            TokenType::For => "for",
+            TokenType::In => "in",
+            TokenType::Loop => "loop",
+            TokenType::Break => "break",
+            TokenType::Continue => "continue",
+            TokenType::As => "as",
+            TokenType::Foreign => "foreign",
+            TokenType::Literal(_) => "literal",
+            TokenType::Identifier(_) => "identifier",
+            TokenType::Error(_) => "error",
+        };
+
+        write!(f, "{s}")
+    }
+}
+
 #[derive(Debug, Clone, PartialEq)]
 pub enum Literal {
     Integer(i32),
diff --git a/sloth/src/main.rs b/sloth/src/main.rs
index 421bbea..a1a4756 100644
--- a/sloth/src/main.rs
+++ b/sloth/src/main.rs
@@ -54,7 +54,18 @@ fn main() {
     // Parsing
     let tokens = Lexer::new(&source).collect_vec();
     let global_symtable = mk_symtable();
-    let mut ast = AstParser::parse(tokens, global_symtable).unwrap();
+
+    let mut ast = match AstParser::parse(tokens, global_symtable) {
+        Ok(node) => node,
+        Err(error) => {
+            eprintln!(
+                "Error in file {} on line {}: {error}",
+                args[1 + (error.line() / 1_000) as usize],
+                error.line() % 1000 + 1,
+            );
+            return;
+        }
+    };
 
     if let Err(error) = analyze(&mut ast) {
         eprintln!(
diff --git a/sloth/src/parser/expr.rs b/sloth/src/parser/expr.rs
index 3decf5d..ac7a19e 100644
--- a/sloth/src/parser/expr.rs
+++ b/sloth/src/parser/expr.rs
@@ -87,7 +87,7 @@ impl<'a> AstParser<'a> {
                 ExprKind::Grouping(Box::new(expr))
             }
 
-            _ => return Err(ParsingError::UnexpectedToken),
+            tt => return Err(ParsingError::UnexpectedToken(self.line, tt, "")),
         };
 
         Ok(Expr::new(
diff --git a/sloth/src/parser/mod.rs b/sloth/src/parser/mod.rs
index a1f251e..09a26fd 100644
--- a/sloth/src/parser/mod.rs
+++ b/sloth/src/parser/mod.rs
@@ -11,8 +11,17 @@ use crate::symtable::SymbolTable;
 pub enum ParsingError {
     #[error("Invalid operation")]
     InvalidOp,
-    #[error("Unexpected token")]
-    UnexpectedToken,
+    #[error("Unexpected token '{1}'. {2}")]
+    UnexpectedToken(u32, TokenType, &'static str),
+}
+
+impl ParsingError {
+    pub fn line(&self) -> u32 {
+        match &self {
+            ParsingError::InvalidOp => 0,
+            ParsingError::UnexpectedToken(x, _, _) => *x,
+        }
+    }
 }
 
 #[derive(Debug)]
@@ -92,10 +101,13 @@ impl<'a> AstParser<'a> {
         self.advance_if(|it| it.tt == *next)
     }
 
-    pub fn consume(&mut self, next: TokenType, error: &str) -> Result<&Token, ParsingError> {
+    pub fn consume(
+        &mut self,
+        next: TokenType,
+        error: &'static str,
+    ) -> Result<&Token, ParsingError> {
         if std::mem::discriminant(&self.peek().tt) != std::mem::discriminant(&next) {
-            println!("{error} at index {:?}", self.index);
-            return Err(ParsingError::UnexpectedToken);
+            return Err(ParsingError::UnexpectedToken(self.line, next, error));
         }
 
         Ok(self.advance().unwrap())
@@ -103,7 +115,7 @@ impl<'a> AstParser<'a> {
 
     pub fn consume_literal(&mut self) -> Result<Literal, ParsingError> {
         let Some(TokenType::Literal(literal)) = self.advance().map(|it| it.tt.clone()) else {
-            return Err(ParsingError::UnexpectedToken);
+            return Err(ParsingError::UnexpectedToken(self.line, self.peek().tt.clone(), "Expected literal"));
         };
 
         Ok(literal.into())
@@ -111,7 +123,7 @@ impl<'a> AstParser<'a> {
 
     pub fn consume_identifier(&mut self) -> Result<String, ParsingError> {
         let Some(TokenType::Identifier(identifier)) = self.advance().map(|it| it.tt.clone()) else {
-            return Err(ParsingError::UnexpectedToken);
+            return Err(ParsingError::UnexpectedToken(self.line, self.peek().tt.clone(), "Expected identifier"));
         };
 
         Ok(identifier)
diff --git a/sloth/src/parser/stmt.rs b/sloth/src/parser/stmt.rs
index d8a0509..6af4634 100644
--- a/sloth/src/parser/stmt.rs
+++ b/sloth/src/parser/stmt.rs
@@ -24,10 +24,10 @@ impl<'a> AstParser<'a> {
         // Consume the foreign token
         self.consume(TokenType::Foreign, "Expected foreign")?;
 
-        match self.peek().tt {
+        match &self.peek().tt {
             TokenType::Fn => self.define_function(true),
 
-            _ => Err(ParsingError::UnexpectedToken),
+            tt => Err(ParsingError::UnexpectedToken(self.line, tt.clone(), "")),
         }
     }